Abstract
Aposematism, the use of conspicuous colours to advertise unpalatability to predators, is perhaps the most studied signalling system in nature. However, its evolutionary stability remains paradoxical. The paradox is illustrated by the problem of automimicry. Automimics are palatable individuals within a population of unpalatable aposematics. Automimics benefit from predators avoiding warning coloration without carrying the models' cost of unpalatability, and should increase in the population, destabilizing the signalling system, unless selected against in some way. Cautious sampling, instead of avoidance, by predators may offer a solution to this problem. Here, we investigate the effect of automimic frequency on predator sampling behaviour, and whether predator sampling behaviour may provide a selection pressure against mimics. Domestic chicks (Gallus gallus domesticus) were subjected to the task of discriminating between green (signalling) and untreated brown chick crumbs. Some of the green crumbs were quinine treated and thus unpalatable. The frequency of palatable signalling prey items varied in four treatments; all unpalatable, low automimic frequency, high automimic frequency and all palatable. The results show that predator sampling behaviour is sensitive to automimic frequency and that predators may discriminate between models and mimics through sampling, and thereby benefit unprofitable prey. The results suggest somewhat surprisingly that aposematic signalling is stable only because of the actions of those predators not actually deterred by warning signals.
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Selected References
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- Andersson M. Why are there so many threat displays? J Theor Biol. 1980 Oct 21;86(4):773–781. doi: 10.1016/0022-5193(80)90310-0. [DOI] [PubMed] [Google Scholar]
- Brower L. P. Ecological chemistry. Sci Am. 1969 Feb;220(2):22–29. doi: 10.1038/scientificamerican0269-22. [DOI] [PubMed] [Google Scholar]
- Brower L. P., Glazier S. C. Localization of heart poisons in the monarch butterfly. Science. 1975 Apr 4;188(4183):19–25. doi: 10.1126/science.188.4183.19. [DOI] [PubMed] [Google Scholar]
- Brower L. P., McEvoy P. B., Williamson K. L., Flannery M. A. Variation in cardiac glycoside content of monarch butterflies from natural populations in eastern North America. Science. 1972 Aug 4;177(4047):426–428. doi: 10.1126/science.177.4047.426. [DOI] [PubMed] [Google Scholar]
- Brower L. P., Pough F. H., Meck H. R. Theoretical investigations of automimicry, I. Single trial learning. Proc Natl Acad Sci U S A. 1970 Aug;66(4):1059–1066. doi: 10.1073/pnas.66.4.1059. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Brower L. P., van Brower J., Corvino J. M. Plant poisons in a terrestrial food chain. Proc Natl Acad Sci U S A. 1967 Apr;57(4):893–898. doi: 10.1073/pnas.57.4.893. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kay D., Rothschild M., Aplin R. Particles present in the haemolymph and defensive secretions of insects. J Cell Sci. 1969 Mar;4(2):369–379. doi: 10.1242/jcs.4.2.369. [DOI] [PubMed] [Google Scholar]
- Kelley Katherine C., Johnson Kelly S., Murray Mitzi. Temporal modulation of pyrrolizidine alkaloid intake and genetic variation in performance of Utetheisa ornatrix caterpillars. J Chem Ecol. 2002 Apr;28(4):669–685. doi: 10.1023/a:1015224407041. [DOI] [PubMed] [Google Scholar]
- Pough F. H., Brower L. P., Meck H. R., Kessell S. R. Theoretical investigations of automimicry: multiple trial learning and the palatability spectrum. Proc Natl Acad Sci U S A. 1973 Aug;70(8):2261–2265. doi: 10.1073/pnas.70.8.2261. [DOI] [PMC free article] [PubMed] [Google Scholar]